1. Field
Example embodiments relate to an oxide semiconductor and a thin film transistor (TFT) including the oxide semiconductor, and more particularly, to a semiconductor material including a material added to an indium oxide, and an oxide TFT including the semiconductor material.
2. Description of the Related Art
Thin film transistors are applied in various application fields, and may be used as switching and driving devices in the field of display and a selector switch of a cross point type memory device.
Because liquid crystal displays (LCDs) are actively being used as television (TV) panels, research into organic light emitting displays has been conducted to be applied to TVs. Display technology for TVs has been developed to meet market demands. The market demands include TVs having a larger size, digital information displays (DIDs), a lower price and/or improved quality (moving picture file expression, high resolution, brightness, contrast ratio, and color reproduction). In order to meet such demands, a substrate formed of a glass, is required to be enlarged and thin film transistors (TFTs) are required to be applied as switching and driving devices of displays to have improved performance.
To form switching and driving devices of displays, amorphous silicon (a-Si) TFTs may be used. Amorphous silicon (a-Si) TFTs may be formed uniformly on a large surface, having a size of about 2 m or greater for a lower price, and thus, are being widely used. However, to be both large-sized and high-quality, displays having high performance switching and driving devices are required. Thus, the use of a-Si TFTs, having mobility of about 0.5 cm2/Vs, may be limited. Thus, TFTs having mobility that is higher than that of a-Si TFTs and a manufacturing method thereof are needed.
Therefore, because polycrystalline silicon (poly-Si) TFTs, having significantly higher performance than that of a-Si TFTs, have higher mobility of several tens to several hundred cm2/Vs, poly-Si TFTs may be applied in higher-quality displays. Deterioration problems are generated less frequently in devices having poly-Si TFTs than in devices having a-Si TFTs. However, in order to manufacture poly-Si TFTs, more complex processes than those of a-Si TFTs are required, thereby adding additional expenses. Thus, poly-Si TFTs may be applied to high quality displays or OLEDs but are not appropriate in terms of cost compared to a-Si TFTs. Thus, application of poly-Si TFTs is limited. Also, in a poly-Si TFT, due to problems, e.g., limitation of manufacturing equipments and defects, manufacturing processes using larger substrates having a size of 1 m or above are not being conducted, and thus, applying poly-Si TFTs to TVs is difficult.
Accordingly, TFT technology having advantages of both a-Si TFTs and poly-Si TFTs is required. Research into TFT technology is actively being conducted and is mainly focused on an oxide semiconductor device.
Zinc oxide (ZnO)-based TFTs are the main focus for use in the oxide semiconductor device. Zinc oxide (ZnO)-based materials may include a Zn oxide, an In-Zn oxide, and oxides doped with Ga, Mg, Al and/or Fe. Because ZnO-based semiconductor devices may be manufactured at a lower temperature and into an amorphous state, ZnO-based semiconductor devices have an advantage in having a large surface area. In addition, a ZnO-based film has higher mobility, and thus, has improved electrical properties when compared with polycrystalline silicon.
Moreover, research into application of indium oxide (InO)-based materials as channel materials of the TFT is also being conducted. In related art, a TFT showing an enhancement mode characteristic, in which an InO material is applied to a channel, is disclosed. Also, in related art, a TFT using a metal oxide semiconductor, wherein the metal oxide includes an InO material, is disclosed. Moreover, related art discloses doping of InO materials with materials, e.g., zinc (Zn), copper (Cu), magnesium (Mg), cobalt (Co), or calcium (Ca), and applying the doped InO materials to channel materials, and doping of an InO material with cerium dioxide (CeO) and applying the doped InO material to the channel material.